This invention relates to time code generators and more specifically to time code generators which will generate serial code sequences for use in biomedical or other data acquisition systems.
Paper recorders and magnetic tape recorders are commonly used to record data in biomedical laboratories and hospitals. It is often necessary to annotate the data with identifying comments such as date of the test, time of the recording, or the event which is being recorded. Paper recordings are commonly annotated by comments written by hand on the recordings as they are generated, or added later from memory. Magnetic tape recordings are annotated with verbal comments if a voice track is available.
Some paper and magnetic tape recorders have an event marker that is an integral part of the instrument. Significant events are indicated on their recordings by manually introduced single or multiple spikes or blips. Event marks, as commonly used, carry limited information. Electronic date and time code generators have been developed to synchronize magnetic tape recorders used in data links in aerospace and other applications. Time code instruments are also used in automatic tape search and data retrieval applications.
Many time code generators are available with a slow-code or oscillographic code output in one or more of at least 50 recognized serial BCD formats. However, the present date and time code generators and the formats which they employ have limitations which are particularly apparent when the instrument is employed in biomedical data acquisition.
Present instruments only generate time codes in a continuously repeating mode of operation and cannot generate a single complete code sequence upon command. The capability of generating either a single frame and/or repeating frames is an important option for a time, date, and event code generator intended for use in a biomedical laboratory. In such an environment, paper and magnetic tape recorders are frequently started and stopped at irregular intervals, and experimental variables and conditions are often changed between recording intervals according to a predetermined protocol. It is important for subsequent data analysis to record the time of day simultaneously in all media each time records are taken, and to index important events with a unique numerical code. Usually one cannot afford to use a data channel to record only indexing codes. The option of brief, single code frames permits one to interlace the indexing codes with physiologic or other data on the same channel. For example, the date might be introduced at the start of the tape or paper recording to identifying the patient, animal, or the experiment. If many brief records are taken at random intervals, e.g. during cardiac catheterization, the time of day might well be recorded at the start of each brief record. If continuous recordings are taken over many hours, for example if a patient undergoing open heart surgery, the time of day would probably be recorded at periodic intervals, perhaps every ten minutes. In addition to periodic time and date recordings, consecutive event numbers might be recorded to index specific events such as the withdrawal of a blood sample, the injection of a drug, measurement of cardiac output, the point at which the patient or experimental animal is switched to extracorporeal blood oxygenation, and the like. The presence of date, time, and consecutive event codes recorded simultaneously in all media facilitates matching of recorded data with the written protocol records, snychronizing events recorded simultaneously by different recording instruments.
Since the standard codes currently used are intended to be used in a continuously repeating mode and to be read by a special time code reading instrument, the code format is not optimized for visual interpretation. The individual groups of data bits are not readily identified, and the individual data bits are often identified manually by counting with reference to special start-frame identification bits included in the code. None of present commerical instruments include a consecutive event number generator that employs the same BCD serial format at the time code portion of the same instrument.